How to use C language to write: Generic Stack

Implementing a simple stack is not difficult, but it is still a challenge to compile a GenericStack in C language. this article uses the auto-increment array method to implement the stack. follow the general design principles of C language written in the previous article ("genericlist.

 

Model

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Core code

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For the complete code, see myGitHub (https://github.com/gnudennis/ds_c) (genric-stack.h
Generic-stack.c generic-stack-test.c)

0. Generic Stack Definition

typedef void *ElementAddr;typedef void (*PfCbFree)(ElementAddr);typedef struct StackRecord{        ElementAddr*array;        intelemsize;        intloglength;        intalloclength;        PfCbFreefreefn;} *Stack;

 

1. API design

/* Create a new stack */Stack stack_create(int elemsize, PfCbFree freefn);/* Dispose the stack */void stack_dispose(Stack stk);/* Make the given stack empty */void stack_make_empty(Stack stk);/* Return true if the stack is empty */int stack_is_empty(Stack stk);/* Insert a new element onto stack */void stack_push(Stack stk, ElementAddr elemaddr);/* Delete the top element off the stack */void stack_pop(Stack stk);/* Fetch the top element from the stack */void stack_top(Stack stk, ElementAddr elemaddr);/* Fetch & Delete the top element from the stack */void stack_top_and_pop(Stack stk, ElementAddr elemaddr);

The purpose of separating pop and top is to meet different needs, and stack_top_and_pop is added as a supplement.

 

2. Implementation

#define MIN_STACK_SIZE (4)/* Create a new stack */Stack stack_create(int elemsize, PfCbFree freefn){        Stack stk;                stk = malloc(sizeof(struct StackRecord));                if ( stk == NULL) {                fprintf(stderr, "Out of memory\n");                exit(1);        }                stk->array = malloc(elemsize * MIN_STACK_SIZE);        if (stk->array == NULL) {                fprintf(stderr, "Out of memory\n");                exit(1);        }        stk->elemsize = elemsize;        stk->loglength = 0;         stk->alloclength = MIN_STACK_SIZE;}/* Dispose the stack*/void stack_dispose(Stack stk){        stack_make_empty(stk);        free(stk->array);        free(stk);}/* Make the given stack empty*/void stack_make_empty(Stack stk){        if ( stk->freefn ) {                int i;                for ( i = 0; i < stk->loglength; ++i) {                        stk->freefn((char *)stk->array +                                     i * stk->elemsize);                }        }        stk->loglength = 0;}/* Return true if the stack is empty*/int stack_is_empty(Stack stk){        return stk->loglength == 0;}static void stack_grow(Stack stk){        stk->alloclength *= 2;        stk->array = realloc(stk->array,                              stk->alloclength * stk->elemsize);}/* Insert a new element onto stack */void stack_push(Stack stk, ElementAddr elemaddr){        ElementAddr target;        if ( stk->loglength == stk->alloclength )                stack_grow(stk);        target = (char *)stk->array + stk->loglength * stk->elemsize;        memcpy(target, elemaddr, stk->elemsize);        stk->loglength++;}/* Delete the top element off the stack */void stack_pop(Stack stk){        ElementAddr target;        if ( stack_is_empty(stk) ) {                fprintf(stderr, "Empty stack\n");                exit(1);        }        if ( stk->freefn ) {                target = (char *)stk->array +                          (stk->loglength-1) * stk->elemsize;        stk->freefn(target);        }        stk->loglength--;}/* Fetch the top element from the stack */void stack_top(Stack stk, ElementAddr elemaddr){        void *target = (char *)stk->array +                        (stk->loglength-1) * stk->elemsize;        memcpy(elemaddr, target, stk->elemsize);}/* Fetch & Delete the top element from the stack */void stack_top_and_pop(Stack stk, ElementAddr elemaddr){        ElementAddr target;        if ( stack_is_empty(stk) ) {                fprintf(stderr, "Empty stack\n");                exit(1);        }        target = (char *)stk->array +                  (stk->loglength-1) * stk->elemsize;        memcpy(elemaddr, target, stk->elemsize);        stk->loglength--;}

Use and Test

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Test code:

#include <stdio.h>#include <stdlib.h>#include <string.h>#include "generic-stack.h"void strfreefn(ElementAddr elemaddr){        free(*(char **)elemaddr);}int main(int argc, char **argv){        Stack int_stk, str_stk;        int i;        char *names[] = {                 "C", "C++", "Jave", "C#", "Python",                 "PHP", "Basic", "Objective C", "Matlab", "Golang"         };        /* test integer stack */        printf("Test integer stack\n");        int_stk = stack_create(sizeof(int), NULL);        for ( i = 0; i < 10; ++i ) {                stack_push(int_stk, &i);        }        while ( !stack_is_empty(int_stk) ) {                int val;                stack_top_and_pop(int_stk, &val);                printf("%d\n", val);        }                stack_dispose(int_stk);        /* test string stack */        printf("Test string stack\n");        str_stk = stack_create(sizeof(char *), strfreefn);        for ( i = 0; i < 10; ++i ) {                char *copy = strdup(names[i]);                char *dest;                stack_push(str_stk, );        }                while ( !stack_is_empty(str_stk) ) {                char *dest;                stack_top_and_pop(str_stk, &dest);                printf("%s\n", dest);                free(dest);        }        stack_dispose(str_stk);        return 0;}

Analysis:

 

(1). int_stack (storage object)

 

(2). str_stack (storing pointers)

Array stores a series of pointers. The actual objects pointed to by these pointers must be allocated in the heap. therefore, the source of objects that are initially put into the stack for management may be heap, stack, or even constant zone. to facilitate management, you should first allocate these objects in the heap (source object copy: The strdup operation above ). "Once an element is put into the stack, the control of this element is handed over to the stack for management. Once an element is output to the stack, the control of this element is handed over to the user for management ".